From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Zhang Subject: Re: [ANNOUNCE] iSCSI enterprise target software Date: Tue, 01 Mar 2005 14:14:47 -0500 Message-ID: <1109704486.2878.23.camel@localhost.localdomain> References: <1109702227.6293.137.camel@laptopd505.fenrus.org> <1109702911.2878.16.camel@localhost.localdomain> <4224BC17.7000103@pobox.com> Reply-To: mingz@ele.uri.edu Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Received: from leviathan.ele.uri.edu ([131.128.51.64]:35003 "EHLO leviathan.ele.uri.edu") by vger.kernel.org with ESMTP id S261990AbVCATPE (ORCPT ); Tue, 1 Mar 2005 14:15:04 -0500 In-Reply-To: <4224BC17.7000103@pobox.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jeff Garzik Cc: Arjan van de Ven , Bryan Henderson , Tomonori Fujita , iet-dev , linux-scsi On Tue, 2005-03-01 at 14:01, Jeff Garzik wrote: > Ming Zhang wrote: > > On Tue, 2005-03-01 at 13:37, Arjan van de Ven wrote: > > > >>On Tue, 2005-03-01 at 10:24 -0800, Bryan Henderson wrote: > >> > >>>One thing that's implicit in your reasons for wanting to be in the kernel > >>>is that you've chosen to exploit the kernel's page cache. As a user of > >>>the page cache, you have more control from inside the kernel than from > >>>user space. The page cache was designed to be fundamentally invisible to > >>>user space. > >>> > >>>A pure user space implementation of an ISCSI target would use process > >>>virtual memory for a cache and manage it itself. It would access the > >>>storage with direct I/O. > >> > >>why would it use direct I/O ? Direct I/O would be really stupid for such > >>a thing to use since that means there's no caching going on *at all*. > >> > > > > what Bryan suggest is a privately owned and managed user space cache. so > > for that disk write should be real write-through. > > > > it is hard to beat linux kernel cache performance though. > > A privately managed user space cache uses Linux kernel cache. what i mean is private cache algorithms. for example, windows request are not page size aligned so some bitmap based cache algorithms might be useful. > > As does mmap/sendfile... > > Jeff >